Nonrotating multipiston radial pump



Sept. 21, 1954 Filed Jan. 9, 1951 E. ORSHANSKY, JR

NONROTATING MULTIFISTON RADIAL PUMP 4 Sheehs-Sheet 1 Sept. 21, 1954 E.ORSHANSKY, JR

Filed Jan. 9, 1951 4 Sheets-Sheet 2 32 0 1114 a 50 67(60 1 4 a lad/ 1717 UK I 19 i9 i2 47 54 .54 V g;

fijz'as Ora/zazzs/iyJn P 1954 E. ORSHANSKY, JR 2,689,532

NONROTATING MULTIPISTON RADIAL PUMP Filed Jan. 9, 1951 4 Sheets-Sheet 3[UVEHi C I' E4205 Ora/zazaslgydm Sept. 21, 1954 E. ORSHANSKY, JR2,639,532

NONROTATING MULTIPISTON RADIAL PUMP Filed Jan. 9, 1951 4 Sheets-Sheet 4Patented Sept 21, 1954 N ONROTA'I'ING MULTIPISTON RADIAL PUMP EliasOrshansky, Jr., Pasadena, Calif., assignor to International BusinessMachines Corporation, New York, N. Y., a corporation of New YorkApplication January 9, 1951, Serial No. 205,050

4 Claims. 1 The present invention relates to a non-rotating multi-pistonradial pump. More particularly, the present invention concerns a radialpump having a plurality of non-rotatable pistons actuated by aneccentrically rotatable hub and sup plied with working fluid bycam-actuated valve means.

Various types of radial pumps have been proposed in the art,particularly for utilization in high pressure hydraulic systems.However, a problem common to all such pumps has been the control ofworking fluid flow to and from the piston pressure spaces. The valvingarrangements of the prior art have been complex, and generally haverequired intricate, close tolerance machining. For example, one of themore commoh types of valving arrangements involves the provision ofinlet and outlet passages in a fixed pintle, and the employment of arotatable barrel mounted on the pintle and carrying the reciprocablepistons thereon for valving coaction with the pintle passages.Thisarrangement has been unsuitable for use at relatively highpressures, due to the extreme accuracy required in machining the pintleand the barrel, and the ever present problem of working fluid leakagetherebetween.

The present invention now provides an ex-,

tremely simple, readily utilized, and easily manufactured and maintainedmulti-piston radial pump. In the pump of the present invention, acylinder block is fixedly positioned within a casing, the cylinder blockhaving interior pressure spaces within which reciprocable, non-rotatablepistons are adapted for movement. Reciprocation of the pistons iscarried out by a hub which is rotatable within the cylinder block andwhich is provided with a peripheral eccentric surface operably connectedto thepistons.

The casing is provided with a pair of inwardly opening, concentric,annular fluid passages, one of the passages communicating with an inletport for the reception of working fluid, and the other passagecommunicating with an outlet port for the reception of working fluidunder pressure from the piston spaces. The cylinder block is providedwith. fluid flow ports, each of which communicates with one of thepassages of the casing, and double-acting valves are also carried by thecylinder blockfor controlling flow from the fluid flow passages into thepiston chambers. These double-acting valves are controlled by rotatablevalve plates which are synchronized with rotation of the eccentric hubsurface, and the valve plates have camming faces which act upon thevalves to reciprocate the same to establish and interrupt communicationof the piston chambers with the inlet passage and the outlet passage insuccession.

In this manner, rotation of the hub controls both ingress and egress ofworking fluid to the piston chambers, and also the subjection of theworking fluid to piston pressures. control insures absolutesynchronization of piston movement and working fluid communication withthe piston chambers.

It is, therefore, an important object of the present invention toprovide an economical, simple, radial piston pump provided with cam-:actuated valving means.

Another important object of the present invention is to provide a radialpiston pump provided with non-rotatable pistons and valve means whichare synchronized for operative movement by rotation of an eccentric hub.

A further important object of the present invention is to provide animproved radial piston pump having annular working fluid flow passagescommunicating with pump piston chambers through double-actingcam-actuated valves journaled for reciprocating movement in a pistoncylinder block.

It is still another important object of the present invention to providea radial piston pump wherein a single rotatable element coordinates andsynchronizes piston pressure movement and valve actuation for fluidinlet and outlet flow.

Yet an additional object of the present invention is the provision of aradial piston pump having a rotatable eccentric hub for actuating aplurality of fluid pressure pistons and for effecting the rotation ofcam actuating plates for a corresponding number of double-acting inletand outlet fluid flow valves.

Other and further important objects of this invention will be apparentfrom the disclosures in the specification and the accompanying drawings.

On the drawings:

Figure 1 is a radial sectional view, with parts shown in elevation,taken along a pair of parallel axially spaced planes of a radial pistonpump of the present invention;

Figure 2 is a vertical sectional view taken along the planes lIII ofFigure 1;

Figure 3 is a horizontal sectional view taken along the planes IIIIII ofFigure 1;

Figure 4 is a fragmentary sectional view, with parts shown in elevation,similar to Figure 3 and illustrating a double-acting valve element inneural position;

This positive Figure 5 is an exploded fragmentary perspective view,partly in section, illustrating a portion of the piston actuatingmechanism of a pump of the present invention;

Figure 6 is a longitudinal sectional view, with parts shown inelevation, of a modified form of radial piston pump of the presentinvention; and

Figure '7 is a sectional view of the pump of Figure 6 taken along theplanes VIIVII.

As shown on the drawings:

One form of pump of the present invention is illustrated in Figures 1-5,inclusive, and this form shall be described first in detail.

The pump casing and hub structure As shown in Figures 1-3, inclusive,the pump of the present invention is indicated in general by referencenumeral ID, the pump including a central, generally cylindrical casingsection i I closed at each axial end by front and rear cover plates l2and 53, respectively. As particularly illustrated, the central casingsection H is provided with annular end faces M and I5 each provided withcircumferentially spaced, inwardly extending threaded apertures it forreceiving screws ll for securing the end plates 52, #3, respectively,thereto.

The end plates l2 and 13 are each provided with inwardly extendingshoulders it which snugly contact the inner periphery of the centralcasing section l i, and which are grooved to retain annular seal ringsis against the central casing section to define a sealed inner space itlying between the plates. The central casing section i i is providedwith an annular inlet groove 25 and an annular outlet groove 22 eachformed in the inner periphery of the casing section ii to providepassages for a working fluid or a hydraulic medium to be utilized inconnection with the pump H3, and that portion of the circumference ofthe central casing section 5 i lying between the grooves 2 l 22 istapered, as at 23, to provide an inner frusto-conical bottoming surface,for a purpose to be hereinafter more fully explained.

As best seen in Figure l, the grove 22 communicates with an outletopening 24 formed in an upstanding embossment 26 integrally cast orformed in the central casing section I I. A similar opening 2? isprovided for communication with the in let groove 2 i.

The end plates 52 and it are provided with centrally located inwardlyprojecting annular bosses 2S and 23, respectively, which extend into thespace 253 and which receive therein a press-fitted outer bearing race33, The bearing races 33 are each in running contact with a plurality ofroller bearing elements 3| which in turn contact inner bearing races 32.The bearings carried by the bosses Z8 and 29 are of substantially thesame size,

and a pump hub 33 is rotatably journaled in the bearings.

The hub 33 is provided with generally cylindrical end portions 34 whichcontact the inner periphery of the inner bearings race 32, so that theradially enlarged central hub section is positioned between the bearingsin the space 20. The central portion of the hub 33 is provided with .aneccentric outer surface 35, and the hub 33 is also provided with acentral bore 36 closed at one end, namely that end adjacent the endplate l3 by a generally cylindrical hub plug 37 having a circumferentialgroove within which a seal ring 38 is positioned. The plug 31 isbott'omed against a shoulder 39 formed in the hub bore and is retainedthereagainst by means of an annular locking ring 40. The other extremityof the hub bore 36 has extending thereinto peripherally spaced, axiallyelongated splines 4| for attachment to a prime mover drive shaft (notshown) or other suitable source of power. Excessive axial movement ofthe hub 33 relative to the bearing races 32 is prevented by means oflock nuts 42 threaded upon correspondingly threaded exterior portions ofthe hub.

That portion of the hub bore 36 carrying the splines 4| is surrounded bya centrally located axially outwardly extending boss l3 formed on thecover plate [2 and provided with an inwardly projecting circumferentialflange lid. The

" hub 43' and the flange 44 serve to retain a pressfitted oil seal 43 insnugly seated relation be tween the cover plate I2 and the adjacentextreme end of the hub 33.

It will thus be seen that the casing sections ll, l2 and I3, cooperateto define the interior space which is sealed, as by seal rings [9, fromthe atmosphere. The cover plates i2 and it serve to journal therein aninteriorly splined pump hub 33 having an interior eccentric cammingsurface 35. Upon rotation of the hub 33, any axial thrust of the hubwill be taken up by the thrust bearings provided by the inner and outerraces and 32 and the rollers or other anti-friction elements 3!therebetween.

Cylinder block and piston structure The rotatable hub 33 has the centraleccentric surface thereof enclosed within a generally cylindricalreactance ring 31, the reactance ring and the hub surface 35 havinginterposed therebetween a plurality of needle bearings 48 providing ananti-friction mounting for the ring. The ring 41 has its inner peripherycentrally recessed, as at 49, to accommodate the interposing of theneedle bearings G3.

The outer periphery of the reactance ring 41 is contacted by a pluralityof piston slipper blocks 50, perhaps best shown in Figure 5. The slipperblocks 50 are provided with curved undersurfaces 5| concentric with andmating with the outer surface 41a of the reactance ring ii. Each of theslipper blocks 50 is centrally apertured, as at 52, to receivetherethrough a connecting pin 53, and each block is provided with aninner lateral extension 54 projecting laterally beyond the pin 53 toincrease the surface contact of the slipper block with the reactancering, while accommodating the positioning of an annular retaining ring55 so as to contact each axial end of each of the pins 53.

There is a pair of spaced slipper blocks 50 associated with each pin 53,and a pair of retaining rings 55 is likewise associated with the pins53, so that this subassembly is symmetrical on each side of the pin. Thespace between each pair of slipper blocks 50 accommodates the insertionof a lower portion 56 of a piston El there between. The portion 56 ofthe piston is apertured, as at 58, to receive the pin 53 therethrough,While the slipper blocks 50 accommodate the pin 53 in a running fit, sothat rotation of the pin within the slipper blocks is accommodated uponrelative movement of the piston-pin subassembly. The outer portion ofeach piston 57 is generally cylindrical in a configuration (Figure 1)and each piston extends into a generally cylindrical piston chamber 5%formed in the cylinder block 60 which surrounds the reactance ring 41.The cylinder block Gil is thus provided with a plurality of radiallyextending piston chambers 59, and each piston chamber 59 is isolatedfrom the adjacent piston chamber so that an independent working area isprovided for each piston.

The cylinder block 60 is also provided with a plurality of valvingrecesses 62 at the outer periphery thereof, these valving recesses beingcentrally located withrespect tothe axial length of the cylinder block,and each being positioned immediately adjacent asingle associated pistonchamber with which the valving recess is in full communication, for apurpose to be hereinafter more fully described. On each side of each ofthe central valving chambers 61, the cylinder block is provided with aperipheral, arcuate valving recess 62, each valving recess 62 being incommunication with the inlet and outlet annular grooves 20 and 22,respectively, and also being in communication with a valvingcrosspassage 53 establishing communication between the valving recesses62 and the valving chambers 5|. Each valving passage 63 is generallycylindrical and extends axially throughout the entire axial dimension ofthe cylinder block.

The cylinder block 50 has a central exterior frusto-conical peripheralsurface 54 which mates with and conforms to the frusto-conical surface23 formed in the central casing section II. The extreme axial ends ofthe cylinder block also contact the central casing section H, as at 65,and the mating frusto-conical surfaces 23 and 64 are urged together by acylindrical spacing element 66 interposed between the casing closureplate I 2 and the cylinder block 60. Thus, the cylinder block is firmlywedged into fixed position within the central casing section II by meansof the mating frusto-conical surfaces 23-64 and the spacer block 66acting thereon.

The cylinder block at its inner periphery is recessed to provide arelatively narrow annular land 90 projecting inwardly toward thereactance member 41 and. recessed at spaced points to provide the innerportions of the piston chambers 59. This land supports the pistons 58against displacement under side thrusts generated by the eccentricity ofthe reactance member 47. Since the land 90 thus supports the pistons, anelongated radial supporting surface is provided without enlargement ofthe cylinder block. The narrow land 90 also accommodates radial movementof the retaining rings 55 on either side thereof.

Valuing structure As best seen in Figures 3 and 4, the hub 33,immediately adjacent the eccentric surface 35 and on each side thereof,is provided with a splined exterior surface 67, each splined surface 51receiving thereon a valve plate 58 having a central aperture receivingthe hub reduced portions 34 therebetween and having interior splinesengaged with the spline surfaces 61 of the hub 33. The

plates 68 are thus positioned on each side, of the eccentric surface 35and the plates have central web portions extending radially outwardlyalongside the connecting pins 53, the slipper blocks 50, and theretaining rings 55. The web portions of the plates 68 carry facing wearplates 68 which contact the retaining ring which serve to urge the sameinwardly to retain the connecting pins 53 in their axial position withinthe apertures 52 of the complementary slipper blocks 5! The outerperipheral portionsof the plates 58 are offset, as at 59a, to provideouter peripheral flanges having inner shoulders 70. The flanges 69a, andparticularly theshoulders Ill, define a 6, rotary camming surface,inasmuch as the shoulders are inclined to a radial plane of the hub 33.Since the plates 68 are splined to the hub 33, the plates and the hubrotate as a unit, and rotation of the plates 53 causes a wobble-plateaction to occour inasmuch as the flanges $9 at any given point in thespace 20 will move axially of the hub 33 as the plate is rotated. Thiswobble-- plate action is utilized to control the valving of the pump ofthe present invention, and the plates 53 are indexed relative to oneanother so that the traveling flanges 58 of the pair of plates arealways parallel with one another. In other words, a constant distancebetween the flanges 59 is maintained despite rotation and wobblingaction of the plates 58.

The valving elements which are controlled by the plates 63 are indicatedgenerally at H and these elements take the form of dumbbell-shapedmembers having a central joining portion 12, enlarged valving heads 13at each end of the central portion 72, and terminal rounded projectionsM. Each valving element 1! is mounted in a cross passage 83 forreciprocation therein and the length of the central portion 12 isslightly less than the distance between the valving recesses 62, asshown in Figure 4. Each valve head T3 is of substantially the samedimension as the associated cross passage 63, and when the valvingelement H is in a central position, as shown in Figure 4, the valvingheads 13 prevent the ingress or egress of working fluid from the inletand outlet passages 2| and 22 to the associated piston chamber 59. Therounded projections 74 are each received by a valve plate slipper block15 which is bottomed against the shoulder Til formed in the adjacentvalve plate flange 69a. The valve plate slipper blocks 15 may preferablybe formed of a bearing material, so that slippage between the flanges 69and the blocks is accommodated upon rotation of the plates 68. The valveelements H are held within the cylinder block 65 against rotation andthe projections 14 similarly hold the slipper blocks 15, while thecurved contact between the projections 14 and the slipper blocksaccommodates pivoting of the blocks relative to the valving element, aswill be necessary upon rotation of the plates 68. Further, the shouldersm are materially longer than the corresponding diniension of the blocks75 to accommodate radial sliding, thus preventing binding of the valveplates 68. i

The valving elements H are reeiprocable within the cross passages 63,and it will be seen from Figure 3 that the plates 68 will cause openingof the elements H to establish communication between the valvingrecesses 52 and the cross passages 53 or, in other words, to establishcommunication between the inlet passage 2! or the outlet passage 22 anda valving chamber 5|. Direct selective communication is establishedbetween the inlet and outlet passages and the piston chamber 58 so thata direct, synchronized control over the ingress and egress of workingfluid'is obtained. In order to insure proper registry of the valvingelements 7! with the passages 62, the hub 33 can be moved axially of thecylinder bloclc 6G by the insertion of shims between the end plates 12and I 3 and the central casing section II.

The modified form of Figures 6 and 7 The modified form of pumpillustrated in Figures 6 and 7 is a relatively small, hand-operatedmodel which, while operating in accord ance with the principleshereinbefore set forth in connection with the embodiment of Figures l-5,inclusive, is much simpler in manufacture and operation, particularlysince relatively high pressures are not generated by utilization of thisform of pump.

. As. an aid in the functional description of Figures 6 and 7, referencenumerals identical with those employed in the description of theembodiment of Figures 1-5, inclusive, are utilized with alphabeticalsuffixes attached to indicate the modified form of these parts shown inFigures 6 and '7.

The modified form of pump is indicated generally by reference numeralIlla, and it will be seen that the central casing section Ila is closedat one end by an exteriorly threaded end cap I3a carrying a seal ring[3a for sealing the interior space 20a defined within the casing. Theother end cap lEa secured thereto by suitable means, with an elongatedterminal boss Bil closed by an end cap 12a secured thereto by suitablemeans, as by screws Ha.

The pump Ilia is provided with an axially extending hub in the form of ashaft 33a, which is the functional equivalent of the hub 33 of the pumpIt hereinbefore described. The shaft 33a is journaled in the casing bymeans of bearings spaced along the length of the shaft, one of thebearings having its outer race scamounted in the end cap Ila forretaining bearing elements Bid in contact with an inner race 32acontacting an adjacent peripheral surface of the shaft. The otherhearing has its outer race 30a contacting the inner periphery of aradially inward shoulder 8| formed in the central casting section I lato contact bearings elements 31 a interposed between the race 322a andan inner race 32a carrying an adjacent portion of the shaft 33d. Oilseals 45a are positioned axially outwardly of the bearings for sealingthe space 20a. within the casing.

The shaft 33 is provided with a central peripheral eccentric surface 35acarrying a reactance member i'ic thereon with roller bearing members Miabeing interposed therebetween. A cylinder block Sta receives thereactance member therein, the cylinder block 36a being provided withpiston chambers 59a receiving therein pistons 57a for radialreciprocating movement upon rotation of the shaft 33a. The pistons El aare provided with an open-topped, generally cylindrical recesses Tbreceiving springs 51c interposed between the bottom of the recesses 51band the adjacent portion of the inner periphery of the central casingsection I la. Thus, the springs 53c serve to urge the pistons 57adownwardly within the piston chambers 53a of the cylinder block 60a.toward the reactance member Ma. The cylinder block 60a is retained inaxially fixed, ncn-rotative position within the casing space 23a bymeans of spacer rings 36d on either side thereof and wedged between ashoulder 8| formed in the central casing section [Ia and the cylinderblock and between the cylindler block and the threaded closure plateI311.

The central casing portion I la is provided with an inlet opening 24aand a discharge opening 21a in full registry with annular inlet andoutlet grooves 22a and 21a, respectively. The cylinder block. Eda isprovided with peripheral, arcuately bottomed valving chambers 6midentical with the chambers 61 hereinbefore described and incommunication with the piston bores 59a and with valving passages 63acommunicating with valving recesses 62c, which in turn are in fullcommunication with the outlet and inlet passages 8. 21a and 22a,respectively. Communication between the recesses 620; and the chambersfila is controlled by means of dumbbell-shaped valving elements Hahaving end portions 14a substantially filling the passages 63a forcontrolling fluid communication of the passages GM with the recesses62a. The valve elements "Ha are each provided with a reduced centralportion 12a for accommodating communication between the passages at therecesses as hereinbefore described in connection with the embodiment ofFigures 1-3, inclusive.

Reciprocation of the valve elements I la is accomplished by means ofradially inclined bearings 82 having their inner races 83 press-fittedinto recesses formed in a bearing ring 34 which is keyed to the shaft33a, as at 85, on either side of the cylinder block 60a. Thus, thebearings 82 are rotatable with the shaft 33a, and upon such rotation awobble-plate action is obtained which is identical with the action ofthe valve plates 65 of the embodiment heretofore described.

Actuation of the shaft 33a is accomplished by means of amanually-actuatable handle 83 provided with a terminal knob 87, so thatthe shaft 33 may be manually rotated to effect reciprocation of thepistons 51a and actuation of the valves 'Ha as hereinbefore explained.

Operation The operation of both embodiments of the pumps as hereinbeforeexplained will be readily evident to those skilled in the art from thedisclosed structure.

Initially, it will be noted that the cylinder block 6E3 is fixed againstrotation and that the pistons 51 are likewise non-rotatable but arereciprocable within the piston chambers 59 provided by the cylinderblock. The pistons are pivotally linked to slipper blocks 50 which arein direct elongated contact with a reactance member 41 and, in thesecond embodiment of the invention, the pistons 5'1 may directly contactthe reactance member Mb. The reactance member is disposed in encirclingrelation upon the eccentric cam surface 35 of the hub 33 or shaft 33a,and rotation of the eccentric member will cause radial movement of thereactance member to actuate the pistons in a radial direction within thecylinder block piston chambers.

The piston chambers 59 are in valved communication with the annularinlet and outlet chambers or grooves 22 and 2!, respectively, so thatcommunication between the fluid flow passages and the piston chamberscould be accommodated at any time if it were not for the unique valvingarrangement of the present invention.

The valving arrangement includes the doubleacting valve H which arefixed against rotation, inasmuch as the valves are journaled in thecross-passages 63. Reciprocation of the valves serves to alternatelyconnect the cross-passages 63 and eventually the piston chambers withthe inlet and outlet by means of camming surfaces which are rotatablewith the piston-actuating ec centric member, the hub 33', or the shaft33a. The camming surfaces of the valving plates affect a completereciprocation cycle of each of the valve elements H during eachrevolution of the hub 33 and each intake and discharge cycle of thepistons 51. Thus, a very simple valving arrangement is provided withabsolute synchronism between rotation of the eccentric driving memberand the valving action being insured, and wear and. tear upon thevalving mechanism is substantially lessened by the holding of the valvesagainst rotation and the elimination of relatively rotatable valvingsurfaces.

The opposing equally sized valve heads [3 present equal inner face areasto working fluid acting thereagainst so that any working fluid pressurethrust upon the valves H is equalized and there is no differential fluidpressure force tending to force the valves in a lateral direction.

It will be understood that modifications and variations may be eflectedwithout departing from the scope of the novel concepts of the presentinvention.

I claim as my invention:

1. A multi-piston radial pump comprising a casing defining a generallycylindrical interior space, a fixed generally cylindrical cylinder blockin said space having radially extending piston chambers, pistons in saidchambers for reciprocation therein, radially inwardly extending slipperblocks carried by said piston for reciprocation therewith, a rotatablehub having an eccentric peripheral surface acting upon said slipperblocks during rotation of the hub to reciprocate said blocks and thepistons associated therewith, said casing having spaced annular inletand outlet fluid flow conduits formed in its inner periphery andcommunicating with a source of Working fluid and a working fluidpressure outlet, said cylinder block having cross-passages communicatingwith the casing passages and with said piston chambers, double-actingreciprocable valves slidably journaled in said cross-passages forreciprocation therein to alternately connect each of said pistonchambers with the inlet and outlet passages of said casing, and annularvalve plates rotatable in synchronism with said hub and having opposingcamming faces inclined with respect to a radial plane of the hub andacting directly upon said valves to reciprocate the same.

2. A multi-piston radial pump comprising a casing defining a generallycylindrical block in said space having radially extending pistonchambers, pistons in said chambers for reciprocation therein, radiallyinwardly extending slipper blocks carried by said piston forreciprocation therewith, a rotatable hub having an eccentric peripheralsurface acting upon said slipper blocks during rotation of the hub toreciprocate said blocks and the pisr tons associated therewith, saidcasing having spaced annular inlet and outlet fluid flow conduits formedin its inner periphery and communicating with a source of working fluidand a working fluid pressure outlet, said cylinder block havingcross-passages communicating with the casing passages and with saidpiston chambers, double acting valve means journaled in the cylinderblock cross-passages for reciprocation therein, said valves havingenlarged heads snugly fitting said cross-passages and terminalprojections extending therebeyond, said valve heads 10 being effectiveto control communication between the casing passages and the pistonchainbers upon reciprocation of the valves, and valve plates carried bysaid hub for rotation therewith and having camming surfaces inclinedwith respect to a radial plane of the hub for sliding engagement withthe valve terminal projections to reciprocate said valves in saidcross-passages.

3. In a pump, a casing, an annular cylinder block in said casing andhaving an integrally formed inwardly projecting reduced thickness land,said cylinder block and the land thereof having registering recessesdefining a plurality of circumferentially spaced open-ended radiallyextending piston chambers, radial pistons in said chambers, a slipperblock for each of said pistons positioned on each side of said cylinderblock land, a transverse pin received by mating apertures formed in saidslipper block and the associated pistons, radial movement or said pinsbeing accommodated by said land recesses, an annular retaining ringabutting each end of each of said pins for movement therewith on eachside of said land, rotatable eccentric means reciprocating said pistons,means providing peripheral inlet and outlet fluid flow passages in saidblock and in said casing communicating with said piston chambers,slidable valve means located in said passages for controlling flowbetween said piston chambers and said flow passages, and cam actuatingmeans acting on said valve means to actuate the same in synchronism withthe reciprocation of said pistons.

4. In a pump, a casing, an annular cylinder block in said casing andhaving an inwardly projecting reduced thickness land, said cylinderblock and the land thereof having registering recesses forming a row ofopen-ended radially extending piston chambers, a piston in each of saidchambers, rotatable eccentric driving means in said casing forreciprocating said pistons, said cylinder block land supporting saidpistons against side thrusts generated by rotation of the eccentricdriving means, means providing peripheral inlet and outlet fluid flowpassages in said block and in said casing communicating with said pistonchambers, slidable valve means located in said passages for controllingfluid flow between said piston chambers and said flow passages, andactuaing means acting on said valve means to actuate the same in.synchronism with reciprocation of said pistons.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,471,117 Orshansky May 24, 1949 FOREIGN PATENTS NumberCountry Date 15,221 Great Britain Aug. 13, 1895

